Contrary to a 2D planar image, a 3D image is similar to a real image a person sees and feels. Thus, a 3D image is a new concept in realistic imaging which improves the level of visual information. A 3D effect is realized through a procedure in which left and right eyes perceive an object with disparity. That is, since a person's two eyes are spaced apart by about 65 mm, they see images in two slightly different directions. At this time, a 3D effect is realized due to the optical phenomenon of binocular disparity. Therefore, a 3D image may be realized by inputting disparate images to an observer's two eyes.
A conventional 3D image display device may be categorized into a 3D image display device using a polarized glasses method and a 3D image display device using a glasses-free method. The 3D image display device using the polarized glasses method realizes a 3D effect by outputting left-eye image and right-eye image having different polarization characteristics through polarizers attached to the polarized glasses so that the left-eye image is projected to a left-eye lens and the right-eye image is projected to a right-eye lens. Such a polarized glasses method is disadvantageous in that an observer must wear the polarized glasses, but is advantageous in that limitations on the viewing angle are relatively small and the manufacturing thereof is easy.
The 3D image display device using the polarized glasses method includes an image display unit and a polarization unit. The image display unit includes a left-eye image display unit and a right-eye image display unit which are alternately disposed to generate a left-eye image and a right-eye image, respectively. The polarization unit changes the polarization states of the left-eye image and the right-eye image generated from the image display unit.
The polarization unit may be manufactured by patterning polarizers corresponding to the left-eye image display unit and the right-eye image display unit, or attaching polarizers to retardation films (optical filters) patterned corresponding to the left-eye image display unit and the right-eye image display unit.
Meanwhile, the patterned polarizer or retardation film may be manufactured by coating a photoresist on a polarizer in which a triacetyl cellulose (TAC) film and an iodized stretched polyvinyl alcohol (PVA) film are laminated, or a retardation film exposing a predetermined portion, and treating the exposed portion with a potassium hydroxide solution so that the phase difference retarding function of the predetermined portion is removed. However, such a conventional method is problematic in that it entails a complicated manufacturing step due to chemical etching, has high manufacturing costs, and has low productivity.
As another method, a patterned optical filter may be manufactured by forming a phase retardation layer on a substrate and removing a portion of the phase retardation layer through a laser or grinder. However, this method is disadvantageous in that precise patterning is difficult and defects easily occur due to damage of the phase retardation layer during laser etching.
Also, the above-described methods are disadvantageous in that it is difficult to form patterns of the polarizer or retardation film in exact correspondence to pixels of the image display unit, and a crosstalk occurrence rate is high due to mismatch between the patterns of the retardation film and the pixels of the image display unit.
In order to solve the above problems, there has been a method which manufactures a patterned optical filter, in which an alignment film and/or liquid crystal materials forming a retardation film are printed on a substrate in specific patterns. More specifically, the patterned optical filter may be manufactured by printing an alignment film on a substrate in specific patterns, performing a rubbing process or a photo-alignment process on the alignment film, and forming a liquid crystal layer on the alignment film. Alternatively, the patterned optical filter may be manufactured by printing an alignment film on an entire surface of a substrate, aligning the alignment film in specific patterns by using a mask, and forming a liquid crystal layer on the alignment film. Alternatively, the patterned optical filter may be manufactured by printing an alignment film on an entire surface of a substrate, aligning the alignment film, and printing a liquid crystal layer in specific patterns. The method for manufacturing the patterned optical filter using the printing process is advantageous in that pixels of the image display unit and patterns of the optical filter may be well matched.
However, the optical filters manufactured by the above-described methods have a structure in which an alignment portion in which the liquid crystal layer is aligned in a specific direction and a non-alignment portion in which the liquid crystal layer is not aligned are alternately arranged. Since the non-alignment portion significantly degrades optical performance as compared with the alignment portion, the use of the optical filters manufactured by the above-described methods degrades the picture quality of the image display device.